For example, assume that you have a virtualized domain controller on a Hyper-V host server. When the Hyper-V host server crashes or encounters a power outage, the Active Directory database may become corrupted, or the virtual machine fails to start, and you may receive an error message that resembles the following:
Go to the More information section for more background information.
Hotfix informationA supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.
If the hotfix is available for download, there is a "Hotfix Download Available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.
Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft website: Note The "Hotfix Download Available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.
PrerequisitesTo apply this hotfix, you must be running Windows Server 2012.
Registry informationTo apply this hotfix, you do not have to make any changes to the registry.
Restart requirementYou do not have to restart the computer after you apply this hotfix.
Hotfix replacement informationThis hotfix does not replace a previously released hotfix.
Windows Server 2012Install update rollup 2855336 on the Windows Server 2012-based Hyper-V host.
Windows Server 2008 R2Install update 2853952 on the Windows Server 2008 R2-based Hyper-V host. Also, install update 2853952 on the guest if the guest is running Windows Server 2008 R2 or Windows 7.
This update is available from Windows Update and the Microsoft Download Center.
|All supported x86-based versions of Windows7||Download the update package now.|
|All supported x64-based versions of Windows7||Download the update package now.|
|All supported x64-based versions of Windows Server 2008 R2||Download the update package now.|
|All supported IA64-based versions of Windows Server 2008 R2||Download the update package now.|
Restart requirementA restart is required for the update to resolve this issue.
Virtual hard disks report to a guest operating system that write-caching is enabled, and disks reject requests to disable write-caching that are made by the guest operating system. This behavior is necessary for the following reasons:
- The underlying storage might have an always-on write cache that cannot be disabled. This is because the virtual disk might be migrated to a different disk on the same host (live storage migration), or to a different host (live migration).
- Hyper-V cannot assume that all virtual machines that are running on the same disk will have the same disk cache settings.
Before the update is installed, when Active Directory would try to disable the disk cache, Hyper-V would incorrectly report that this operation was successful. Then, Active Directory would perform file operations under the assumption that no caching was occurring, even though caching was occurring.
After you install this update, Active Directory will try to disable the disk cache, and Hyper-V will correctly report that this is not possible. Then, Active Directory will enable FUA (Force Unit Access) to make sure the data is not cached.
When Active Directory tries to disable the disk cache, event ID 1539 is logged.